This invention relates to a wind power generation system that includes a series of high temperature superconducting (HTS) coils and a direct drive turbine ring generator system.
Air moving relative to the surface of the earth, with an air mass or air load, holds kinetic energy. To extract that energy, a specific arrangement of turbine rotors or blades is required to generate electric power from the kinetic energy inherently stored in wind. Wind energy is defined herein as a moving molecular mass of air, O2, made up of air molecules and traveling at a specific velocity and having a kinetic energy of alpha=@.
Current wind generation turbines are predominantly limited in overall design and performance by mechanical, material, aerodynamic and physical laws. The current art is further limited by design constraints of essentially four elements of the current wind generator design. These four constraint elements include the hub/drive shaft mechanism, the gearbox mechanical design, the wind generator rotor blades, and the turbine generator. In current wind turbine design, these four constraining elements are typically mounted and centered on a load bearing drive shaft that connects the generator, on the rearward portion of the drive shaft, through a gear box and into a hub, with the blades coming out tangentially therefrom. With current art, typically three blades are used to provide the necessary power to rotate the power generating equipment.
A mass airflow approaches the turbine rotor airfoils or blades at atmospheric pressure and ambient temperature for a given wind site with velocities in the range of 40 to 95 feet/second. Upon striking the wind generator airfoil shaped blades at a constant velocity this air mass creates a tangential velocity and force vector that drives the blades rotationally. The direction of rotation is equal and opposite to, the lower-pressure higher-velocity air traveling along the top of the convex airfoil shape blade, compared to the mass airflow traveling at a lower-velocity higher-pressure air traveling along the flat bottom of the airfoil shape.
The blade(s) may be designed to carry the swept area mass load of air flow against the blade(s). The Performance Power Coefficient, Cp, is the ratio of the power in the rotor compared to the power in the wind. Cp is based on the stream tube concept for a mass of air approaching the blades by evaluating the power in the wind, and the extraction of that power from the wind by impacting on the rotating blade mass. The rotor, as it is moved by the airfoils, extracts this power. However, there are significant kinetic energy losses due to turbulent losses at the airfoil. In particular, turbulence and a wake vortex which comes off the tips of the airfoils are among the largest losses of the airfoil blade system. The stream tube of the air mass expands in volume behind the turbine rotor blades as the mass of air is slowed in velocity, resulting in a volume increase. The degree to which the air is slowed by the rotor, as compared to free stream air is termed the axial induction factor. This factor is represented by the mathematical equation below:
  a  =                    U        ⁢                                  ⁢        1            -              U        ⁢                                  ⁢        2                    U      ⁢                          ⁢      1      where “a” is the axial induction factor, “U1” is the wind speed far away from the rotor, “U2” is the wind speed at the rotor. Due to the Law of Conservation of Mass, the air that passes through the rotor does not slow down, therefore a pressure drop across the airfoils is observed and an increase in the volume of air occur, as it expands, as the energy is extracted from the wind by the pressure drop. The air behind the turbine rotor is at sub-atmospheric pressure, the air in front of the turbine rotor is at a pressure higher than atmospheric pressure. The higher pressure in front of the turbine is what deflects some of the air around the turbine.
The maximum coefficient of power is the ability of a wind turbine to extract kinetic energy from the mass air flow across the turbine rotor and is defined by the Betz Limit. The Betz Limit is a function of the Law of Conservation of [Axial] Momentum whereby the wind turbine applies a thrust force on the mass air flow (otherwise the Law of Conservation of Energy would be violated) and consequently the pressure difference between the front to the back of the turbine rotor causes the thrust force that causes the rotation of the blades. The second element of the Betz Limit is the Law of Conservation of Mass and is used to relate to the incoming air to the rotor and the out going air from the rotor. Velocities of the far field flow and near field flow are solved according to the Conservation of Mass and as previously described, the conservation of axial momentum which defines the axial induction factor for the far field flow, the velocities of these flows, and are described in the equations below:U2=U1(1−a)U4=U1(1−2a)“U4” is the wind velocity of the far wind wake. The ability of a wind turbine to extract energy from the wind is defined further by the Coefficient of Power, or Cp, which is also an element of the Betz Limit, this being the derivative of the formula for Power. The formulas for these power definitions are below:Power=P=0.5 pAU2(U2−U4/2)Coefficient of Power=Cp=P/0.5 pAU1/3
The Betz Limit is defined by the maximum value of the formula for “Cp”, whereby the respective velocity relations (near field and far field) are put into the Power formula, and these substituted into the Coefficient of Power formula and is expressed in the equation:Cp=4a(1−a)2
Currently, wind generator systems have a maximum Betz limit of approximately 59.25%. This is basically the maximum efficiency of power extracted from the turbine rotor due to the manifestation of the differing velocities of near field and far field flows, and the differential pressures created by these flows in front of the turbine and behind the turbine.
Thus, it would be advantageous to develop wind generating systems that are able to provide improved efficiency.